Extrusion molding is mainly used for extrusion molding of plastic articles, such as fibers, films, tubes, rods, plates and profiles, with the same cross-section, but cannot mold plastic articles with variable cross section. Plastic articles having small hollow channels, such as medical microtubules, hollow fibers, etc., can also be made by extrusion molding. The common method for extrusion molding of plastic articles having small diameter hollow channels generally includes the steps of installing a hollow core in an extrusion die, and introducing an injection fluid that is generally air or compressed air into the hollow core. For example, Mackley et al. of Cambridge University proposed a molding method of micro-channel film including a plurality of parallel capillary channels (WO 2005/056272), and Wu Daming et al. proposed a molding method of plastic articles including small bore therein (CN 200310101653.0). However, the hollow channels formed in these molding methods have constant inner diameters, and it is difficult by these methods to form hollow channels having dynamically variable diameters.
The molding methods of corrugated plastic pipes can achieve dynamic variability of the hollow channel, but these methods have the following disadvantages: (1) the inner diameter of the channel is generally large, and thus cannot be processed at micron scale; (2) variability of the channel is achieved by a follow-up mechanical molding device, and thus its inner diameter has less varying patterns; (3) the outer diameter of the channel also dynamically varies; and (4) these methods only apply to single-channel pipes.
Device and method for dynamic extrusion molding of plastic articles having variable micro-channel according to the present invention can remedy disadvantages of the above methods: the micro-channel is formed in one-step extrusion molding and has dynamically variable inner diameter while the external diameter is basically invariable; a large number of variable micro-channels can be integrated together; the varying patterns of these variable micro-channels can be conveniently adjusted.